Hi all im new here, dont even know if this is the right place to post my question but here goes

I have recently aquired an old xl250r 1983 model in not a bad shape, i got the engine running again but now im tryin to sort out the electrics, lights and so on, now my questions is this, what should i be looking for when ghe bulbs keep blowing on the bike, cause the lights work when the bike idles but when i crack the throttle just a littel bit it blows the bulb, i only have the headlight bulb connected at the moment, i also dont have a battery connected, dont know if its needs the battery, maybe to act as abuffer or something to keep the voltages at 12v?

I suspect maybe the regulator/rectifier that maybe bad? Any easy way of checking?